A novel GST isoenzyme was purified from hepatopancreas cytosol of Atactodea striata with a combination of affinity chromatography and reverse-phase HPLC. The molecular weight of the enzyme was determined to be 24 kDa by SDS-PAGE electrophoresis and 48 kDa by gel chromatography, in combination with GST information from literature revealed that the native enzyme was homodimeric with a subunit of M-r 24 kDa. The purified enzyme, exhibited high activity towards 1-chloro-2,4-dinitrobenzene (CDNB) and 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl). Kinetic analysis with respect to CDNB as substrate revealed a K-m of 0.43 mM and V-max of 0.24 mumol/min/mg and a specific activity of 108.9 mumol/min/mg. The isoelectric point of the enzyme was 5.5 by isoelectric focusing and its optimum temperature was 38degreesC and the enzyme had a maximum activity at approximately pH 8.0. The amino acid composition was also determined for the purified enzyme. (C) 2003 Elsevier Inc. All rights reserved.